My code:

if(Restitution < 0  || Restitution > 1 || Hardness < 0 || Hardness > 1) 
return false; 
return true;

In reflector:

return (((this.Restitution >= 0f) && (this.Restitution <= 1f)) && ((this.Hardness >= 0f) && (this.Hardness <= 1f)));